Performance of masonry blocks incorporating Palm Oil Fuel Ash

Journal of Cleaner Production 78 (2014) 195e201

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Journal of Cleaner Production
journal homepage: www.elsevier.com/locate/jclepro

Performance of masonry blocks incorporating Palm Oil Fuel Ash
Muhammad Ekhlasur Rahman a, *, Ang Lye Boon b, Agus Setyo Muntohar c,
Md Nafeez Hashem Tanim d, Vikram Pakrashi e
a

School of Engineering and Science, Curtin University Sarawak, CDT 250 98009 Miri, Sarawak, Malaysia
Civil & Construction Engineering Department, Curtin University Sarawak, Malaysia, CDT 250 98009 Miri, Sarawak, Malaysia
c
Department of Civil Engineering, Universitas Muhammadiyah Yogyakarta, Jl. Lingkar Selatan, Taman Tirto, Yogyakarta, Indonesia
d
Dept. of Industrial & Manufacturing Engineering, University of Texas Arlington, USA
e
Dynamical Systems and Risk Laboratory, Dept of Civil Engineering, School of Engineering, University College Cork, Cork, Ireland
b

a r t i c l e i n f o

a b s t r a c t

Article history:
Received 3 November 2013
Received in revised form
26 April 2014
Accepted 26 April 2014
Available online 9 May 2014

This paper presents an experimental study on the development of masonry block with Palm Oil Fuel Ash
(POFA) as a partial replacement to cement whilst maintaining satisfactory properties of masonry block.
The dosages of POFA are limited to 0%, 20%, 40% and 60% by mass of the total cementitious material in the
masonry block. The experiments on masonry block investigate the compressive strength and the
breaking load for mechanical properties and water absorption and efflorescence for its durability. The
compressive strength and the breaking load of the masonry blocks reduce with increasing percentage of
POFA replacement. However, it satisfies the requirements of Class 1 and Class 2 load-bearing masonry
block according to Malaysian Standard MS76:1972. In terms of durability of the masonry block, water

absorption for all the masonry blocks satisfies the requirement of ASTM C55-11 and there is no any sign
of efflorescence on all the masonry blocks. POFA based masonry block are also found to be cheaper than
the cement sand masonry blocks. The experimental studies indicate that POFA based masonry block has
a significant potential for application in the construction industry.
Ó 2014 Elsevier Ltd. All rights reserved.

Keywords:
Masonry block
Waste material
Palm Oil Fuel Ash

1. Introduction
Masonry blocks such as bricks are well known to be one of the
very old and strongest building materials. The blocks are durable
and usually require low maintenance (Sousa et al., 2014). Masonry
blocks normally are made of clay minerals (Da Silva Almeida et al.,
2013) and their application is not limited buildings, due to their
popular usage in different types of walls, monuments and other
variety of structures (Del Coz Diaz et al., 2007). Even now, masonry
blocks are extremely popular for a wide range of construction

around the world and are considered as a demanding construction
material. Developing countries like Malaysia are undergoing significant infrastructural change and the related demand for masonry
blocks is thus very high. The ingredients of masonry block used in
Malaysia are sand, cement and water. The cement production industries are liable for approximately 7% of the world’s carbon dioxide emission. Consequently, the environmental impact including
the carbon footprint of masonry block is significant.

* Corresponding author. Tel.: þ60 85 443939x3816.
E-mail address: merahman@curtin.edu.my (M.E. Rahman).
http://dx.doi.org/10.1016/j.jclepro.2014.04.067
0959-6526/Ó 2014 Elsevier Ltd. All rights reserved.

Parallel to the infrastructure boom, Malaysia’s agricultural
sector has also been developing over time. Palm oil is popular
vegetable oil for cooking and food processing (Oosterveer, 2014)
and Malaysia is one of the world’s largest producers and exporter of
palm oil in the world (Yusoff, 2006). As a result, a very significant
amount of biomass including empty fruit branch, oil palm shell and
POFA are generated every year and it is anticipated to generate
about 100 million dry tonnes of solid biomass by 2020 (National
Biomass Strategy 2020, 2011). For every kg of palm oil produced,

approximately four kg of dry biomass is produced (Ng et al., 2012).
POFA is a by-product of palm oil industry and is generated from the
combustion of empty fruit branch and oil palm shell. Reuse of POFA
in masonry block attempts to utilize solid biomasses from the palm
oil industry. Utilization of waste materials from palm oil industry in
any composite material will enhance the sustainability as well as
will solve an environmentally waste problem issue (AL-Oqla and
Sapuan, 2014).
Many researchers have carried out study on masonry blocks
using waste materials. Ling and Teo (2011) reported on the potential use of waste rice husk ash (RHA) and expanded polystyrene
(EPS) beads in producing lightweight concrete bricks and found
that the properties of the bricks are mainly influenced by the

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content of EPS and RHA in the mix and also the curing condition.
Muntohar and Rahman (2014) presented the use of oil palm shell
waste as masonry block material and found that the maximum

strength was obtained by mixing proportion of 1C: 1 sand: 1 OPS.
Cicek and Tanrıverdi (2007), Chindaprasirt and Pimraksa (2008)
reported that it is possible to produce good quality bricks from fly
ash due to pozzolanic properties of fly ash. Shakir et al. (2013)
investigated bricks incorporating fly ash, quarry dust, and billet
scale and summarised that bricks can be made using these waste
materials. Fernández-Pereira et al. (2011) studied bricks made from
gasification ash and compared with typical values for commercial
bricks and concluded that the bricks could be used commercially.
Turgut (2012) used limestone powder, class C fly ash, silica fume
and water in masonry brick production and found that the
compressive and flexural strengths of the samples containing silica
fume were found to increase significantly when the silica fume
content in the mixtures was increased. Gokhan and Osman (2013)
investigated the effects of rice husk on the porosity and thermal
conductivity properties of fired clay bricks and found that samples
with coarse rice husk have lower thermal conductivity than samples with ground rice husk. Rahman (1987) made bricks from claysand mixes with different percentages of rice husk ash burnt in a
furnace at different firing times and concluded that light weight
bricks could be made from rice husk ash without compromising the
quality of the bricks. Malhotra and Tehri (1996) carried out study on

granulated blast furnace slag based bricks and found that good
quality bricks can be produced from a slag-lime mixture and sand.
Bilgin et al. (2012) investigated the application of waste marble
dust as an additive material in industrial brick and found that the
marble dust as an additive had positive effect on the physical,
chemical and mechanical strength of the produced industrial brick.
Weng et al. (2003) investigated bricks made from dried sludge
collected from an industrial wastewater treatment plant and found
that brick shrinkage, water absorption, and compressive strength
decreased with increasing of the sludge content. Faria et al. (2012)
reported that recycled sugarcane bagasse ash waste could be used
as filler in clay bricks. Gencel et al. (2013) investigated bricks made
from clay with ferrochromium slag and natural zeolite and found
that the mechanical strengths of bricks were increased and thermal
conductivity of samples was decreased than control bricks. Ismail
et al. (2010) carried out study on disposed paper sludge and POFA
based masonry block. The dosages of paper sludge and POFA were
0%, 5%, 10%, 15%, 20% & 25%. It was found that paper sludge-POFA
brick made with 60% cement, 20% sludge and 20% POFA satisfied
the strength requirements of BS 6073 Part 2: 2008 and that the

amount of copper as well as lead resulting from leaching were
within the acceptable limits of Malaysia Environmental Waste
Disposal Act.
Some studies exist on POFA based self compacting concrete
(SCC) and normal vibrating concrete. Fresh concrete properties of
POFA based SCC have been investigated (Safiuddin et al., 2010)
where the dosage of POFA was limited to 15% by mass of the total
cementitious material. It was found that the filling ability and
passing ability decreased and sieve segregation resistance
increased with increasing POFA content. Strength, modulus of
elasticity and shrinkage of concrete incorporating POFA have also
been studied by researchers (Awal and Hussin, 2009). Laboratory
test data based on short-term investigation revealed that the
modulus of elasticity of POFA concrete in association with its
compressive strength was somewhat lower than that of OPC concrete and the shrinkage strain of POFA concrete was higher than
that of OPC concrete. Some investigations into strength increase
through the use of POFA in concrete have been studied (Weerachart
and Chai, 2010) and it was found that the compressive strength of
the concrete increased with the fineness of POFA. Laboratory tests

were conducted to evaluate the performance of palm oil fuel ash in
concrete and it was found that POFA has a potential in suppressing
expansion due to alkaliesilica reaction (Awal and Hussin, 1997),
controlling heat of hydration of concrete (Abdul Awal and Shehu,
2013), and increased durability and sulphate resistance (Chai
et al., 2007). Additionally, the strength & durability properties of
high-strength green concrete (HSGC) containing up to 60% of ultrafine POFA have been studied and it was found that ultrafine POFA
has the potential to produce HSGC (Johari et al., 2012).
It is observed from existing literature that significant research
work exist on masonry block incorporating different types of waste
material based ash including limestone powder, fly ash, silica fume,
RHA, quarry dust, gasification ash, and sugarcane bagasse ash.
Different parameters have been determined in these investigations
but compressive strength and water absorption have been determined by most researchers. Although different types of waste
material have been used to produce brick for research purposes,
commercial production and application is still limited due to lack of
standard guidelines. Further research and development are needed
to develop guidelines for masonry block incorporating waste material (Zhang, 2013). It can also be seen from the literature review
that there are significant research work have been conducted on
SCC and normal vibrating concrete incorporating POFA due to their

pozzolanic properties.
As per the best knowledge of the authors, there is no existing
work on the development of masonry blocks solely employing
POFA and it is expected that this research will create the technical
background for the development and implementation of such
blocks leading to cleaner production in this construction industry
sector. This is particularly impactful for geographical regions in the
world exposed to anthropogenic pollution due to a booming construction sector or for countries those can expect to see a high
industrialisation rate leading to a rapid expansion of construction
(Rahman et al., 2014; Taaffe et al., 2014), where measures such as
that proposed in this paper can act as an active measure towards
controlling pollution employing local resources.
This paper experimentally studies POFA based masonry blocks
by examining their mechanical and durability properties. The experiments on masonry block investigate the compressive strength,
density and the breaking load for its mechanical properties and
water absorption and efflorescence for its durability. The
compressive strength and the breaking load test are also conducted
under soaked or unsoaked condition. Additionally cost analyses of
masonry block and carbon footprint discussion are also presented.
2. Experimental program

2.1. Materials
The materials used for the production of masonry blocks are
water, cement, POFA and river sand. All materials are available
locally and POFA is a free of cost.
2.1.1. Ordinary Portland Cement (OPC)
Ordinary Portland Cement (OPC) grade 42.5 based on ASTM:
C150/C150M e 12 was used in concrete as cementitious material.
The particle density of the cement is 2950 kg/m3 and specific
gravity of 3.14. The Blaine specific surface area was 3510 cm2/g.
2.1.2. Palm Oil Fuel Ash (POFA)
POFA was obtained from a nearby palm oil mill at Lambir, Miri,
Sarawak, Malaysia. The POFA obtained was sieved to 75 mm in the
laboratory to remove coarse particles. This is to ensure that only
small particle sized POFA were used to obtain a better control over

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M.E. Rahman et al. / Journal of Cleaner Production 78 (2014) 195e201

manufacturing masonry blocks. The sieved POFA was stored in a

clean, dry and air tight in a humidity controlled room.
2.1.3. Local river sand
The sand used for the masonry block is local river sand. A sieve
analysis was carried out to determine if this local river sand complies with the AS 2758.1 (1998). The fineness modulus of the local
river sand was calculated to be 1.34. Fig. 1 show the local river sand
grading curve from the analysis and it is observed that 100% sand
passed through 600 mm, indicating that the maximum size the
particles is 600 mm. The particle size distribution curve is also
steeper as the particle size range is smaller which describes poorly
graded sand. From Fig. 1, it can also be seen that most part of the
sample curve falls within the upper limit and lower limit as
required by the AS 2758.1 (AS 2758.1, 1998). Using the tolerance
given in this standard, the sample curve is considered to be
acceptable. Consequently, the local river sand was deemed appropriate for use in the production of the masonry blocks.

Batch

Ratio

Testing date

B1

C:S ¼ 1:3 (Control)

B2

C þ POFA(60%):S ¼ 1:3

B3
B4

C þ POFA(40%):S ¼ 1:3
C þ POFA(20%):S ¼ 1:3

56
28
56
28
28
28

days
days
days
days
days
days

Table 2
Testing program.
Batch Testing date Compression Breaking Water absorption Efflorescence
B1
B2
B3
B4

56
28
56
28
28
28

days
days
days
days
days
days

Y
Y
Y
Y
Y
Y

N
Y
N
Y
Y
Y

Y
Y
Y
Y
N
N

N
Y
N
Y
Y
Y

*Y ¼ Yes, N ¼ No.

2.2. Masonry block mix design
Four batches of masonry blocks were made where the OPC was
partially replaced with 0%, 20%, 40% and 60% POFA by binder
weight. The dimension of each masonry block was 200 mm long,
100 mm wide and 70 mm thick. Table 1 and Table 2 show the
masonry block mix ratio and testing regime. The masonry blocks
were tested at the end of 28 d since the cement paste takes 28 d of
curing to reach around 80% of its total strength. The cement paste
hardens over time, initially setting and becoming rigid and gaining
strength over time starting from a relatively weak condition. The
masonry blocks were also tested at the end of 56 d to determine the
relatively long term effects. Compressive strength test, breaking
load test, water absorption test and efflorescence test were carried
out. These tests were based on the ASTM C55-11 (ASTM Standard
C55, 2011), a normative document on standard test methods for
sampling and testing masonry blocks and structural clay tiles.
2.3. Preparation of masonry blocks
The method of production for the masonry blocks in this project
was through simple blending and compressing. It did not involve
heating and thus carbon emission was not present. First, cement
and sand were measured and blended using a Hobart A200 mixer
in order to obtain a homogenous mixture. Next, the POFA was
measured and added into the mixture to be blended. While
blending, water was constantly added into the mixture until a
homogenous mixture was obtained. The entire mixing process

Cumulative Percentage Passing (%)

Table 1
Brick mix ratio.

takes approximately 15e20 min. Upon obtaining the homogenous
mixtures, they were placed into 200 mm  100 mm  70 mm
timber masonry block moulds. The samples were tamped manually
by hand compaction. To further compact the masonry blocks, the
mixtures in the mould were compacted using a compaction machine (Fig. 2). The specimens were dismantled from the mould and
were cured. Once made, the masonry blocks were kept in
controlled rooms (Fig. 3) for either 28 d or 56 d, where they were
wrapped with plastic.
2.4. Testing methods
The testing method was divided into two categories corresponding to the soaked and unsoaked condition of the masonry
blocks. The difference between the two categories is that the
soaked masonry blocks were subjected to water absorption test. For
the soaked masonry blocks, the experimental program started with
the water absorption test once the masonry blocks reached the
required age, at the end of 28 d or 56 d. Once the water absorption
rate was obtained, the masonry blocks were tested accordingly for
compressive strength or breaking load.
2.4.1. Compression test
The compressive strengths of the masonry blocks at the age of
28 d and 56 d were measured. The test was carried out using a
Universal Testing Machine (UTM). The masonry block specimens
were placed so that the load applied is perpendicular to the surface

100.00
90.00
80.00
70.00
60.00
50.00
40.00
30.00
20.00
10.00
0.00
75 μm

150 μm 300 μm 600 μm 1.18 mm 2.36 mm 4.75 mm 9.5 mm
Particle Size
sample

upper limit

lower limit

Fig. 1. Local river sand grading curve.

Fig. 2. The setup of Compressed Hydraulic Machine used in this study.

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M.E. Rahman et al. / Journal of Cleaner Production 78 (2014) 195e201

The surface water of the specimens was wiped off with a damp
cloth and the weights of the specimens were again weighed and
recorded as Ws after removing the specimen from the submerged
condition. The water absorption of each specimen in percentage
was computed as

Absorption; % ¼ 100ðWs

Fig. 3. Compacted specimens.

bed of the masonry block. A constant loading rate of 1.25 mm/min
was applied to conduct the test and the load was applied to the
masonry block until the failure of the specimen. The failure load for
the specimen was recorded and all pertinent details regarding the
failure were observed. Compressive strength of each specimen was
calculated in MPa (N/mm2) as

C ¼ W=A

(1)

where C is the compressive strength, W is the maximum load
indicated by the universal testing machine and A is the average
gross area of the upper and lower bearing surface of the specimen.

2.4.2. Breaking load test
The breaking load of the masonry blocks at the age of 28 d and
56 d were obtained. The test was also carried out using the Universal Testing Machine where the masonry block specimen was
placed so that the load applied was perpendicular to the bed surface of the masonry block. The specimen was supported with solid
steel rods at the underside while the load was applied at the middle
span of the masonry block. A constant loading rate of 1.27 mm/min
was set to the testing machine. The load was applied to the masonry block through a steel bearing plate until the failure of the
specimen. The failure load for the specimen was recorded and all
pertinent details regarding the failure were observed. The breaking
load of each specimen was calculated in terms of N/mm as

p ¼ P=w

(2)

where p is the breaking load per width, P is the transverse breaking
load obtained from the machine and w is the width of the masonry
block specimen.

(3)

Wd Þ=Wd

2.4.4. Efflorescence test
Efflorescence test was carried out to determine if efflorescence
occurs at the surface of the masonry blocks at the ages of 28 d and
56 d. The first test masonry block specimen was partially immersed
in a tray with distilled water to a depth of approximately 25 mm for
7 d in the drying room. The second test masonry block specimen
was stored in the drying room without contact with water for 7 d.
At the end of 7 d, both specimens were inspected before oven
drying for 24 h. All observations were recorded.
The efflorescence effect of each specimen was observed on all
faces from a distance of 3 m under an illumination of not less than
50 foot candles by an observer with normal vision. Under these
circumstances if no difference is noted, the specimen is considered
not to have effloresced. On the contrary, if perceptible differences
due to efflorescence were noted, the specimen is recorded as
effloresced.
3. Results and discussions
3.1. Density
A higher density of a masonry block is indicative of closely
packed particles. Fig. 4 shows the average densities of masonry
block. It can be seen in the Fig. 4 that the density decreases with
increasing POFA contents as POFA has a lower density. The decrease
in dry density with 20%, 40% and 60% POFA are 5.4%, 5.8% and 8%
indicating that by adding POFA it would be possible to produce
lighter weighing masonry blocks. In compliance with ASTM C55-11
(2011), batch 1 (0%), batch 3 (40%) and batch 4 (20%)masonry blocks
are considered as normal weight masonry blocks as they are all
above 2000 kg/m3. Only batch 2 (60%) is considered as medium
weight masonry block as the density is within 1680e2000 kg/m3.
Overall, POFA masonry blocks are found to be lighter than cement
sand masonry blocks.
3.2. Compressive strength
The compressive strength of the masonry blocks are shown in
Figs. 5 and 6. The graphs show that the compressive strength of the
masonry blocks is affected by the POFA replacement, aging and
immersion.

2200
2100
Density, kg/m3

2.4.3. Water absorption test
The water absorption rate was determined before being tested
for compression, breaking load or efflorescence. The masonry block
specimens were weighed and the weight was recorded as Wi. The
specimen was then dried in a ventilated oven at 110  C for at least
24 h. The weight of the specimen was then recorded as Wd. After
drying, the specimen was cooled in a drying room at 25  C with
relative humidity was around 70%. The specimens were then stored
to be free from air draft and were un-stacked and separately placed
for 4 h until the surface temperature was approximately 28  C,
which was equal to that of the drying room. The specimen was then
submerged in clean water at 30  C for 24 h.

2000
1900
1800
1700
1600
1500
0%

20%
40%
POFA Content

Fig. 4. Average densities of different mixes.

60%

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M.E. Rahman et al. / Journal of Cleaner Production 78 (2014) 195e201

3.2.2. Effect of POFA replacement
The compressive strength results with different percentages of
POFA are presented in Fig. 6. The percentages of POFA are 0%, 20%,
40% and 60%. It can be seen from the Fig. 6 that the compressive
strength decreased with increasing of POFA content. The reason
most likely behind this occurrence is due to the fineness of the
POFA particles. The raw POFA used was sieved to 75 mm, which is
coarser than ground POFA and hence can be associated with lower
compressive strength. The fineness of POFA is related to its microfilling ability that fills micro-voids between cement particles and
eventually contributes to an increase in the compressive strength
(Awal et al., 2010).
The coarseness of raw POFA for this project resulted in larger
voids that led to lower compressive strengths (Muntohar and
Rahman, 2014). Larger particle sizes have higher porosity that increases the actual water/binder ratio and thus resulting in lower
compressive strength (Safiuddin et al., 2011). Additionally, finer
particles have higher surface area, which affects the pozzolanic
activity (Awal et al., 2010) and hence, the compressive strength.
Likewise, the use of larger particles led to more voids, resulting in
lower compressive strength.
3.2.3. Effect of immersion
In terms of soaked and unsoaked masonry blocks, Fig. 6 also
shows that unsoaked masonry blocks produced higher compressive
strength than the soaked masonry blocks. The low compressive
strength of the soaked masonry blocks might be due to loss of
strength during submersion through water absorption which
softens the matrix.
3.3. Breaking load

18
16

Compressive Strength, MPa

3.2.1. Effect of aging
The results of 28 d and 56 d compressive strength are shown in
Fig. 5. The age of the masonry block plays an important role for the
compressive strength as a higher age corresponds to a higher
compressive strength. Fig. 5 shows that the strength of 56 d masonry blocks is higher than those of 28 d. The reason can be
attributed to the slow pozzolanic activity of the POFA (Safiuddin
et al., 2011). Additionally, the cement also continuously reacts
with time producing more CSH gel, which gives more strength to
the masonry block. The pozzolanic activity slowly diminishes the
calcium hydroxide content from the hydration process though reaction with silicon dioxide from the POFA (Ahmad et al., 2007) and
produces more CSH gel. As a result the compressive strength also
increases with the increasing of time.

10

B1 Soak
B2 Unsoak

B2 Soak

8

6
4
2
0
0%

20%

40%

60%

POFA Content
Fig. 6. Average compressive strengths of masonry blocks at 28 d for soaked and
unsoaked conditions.

compressive strength whereby breaking load is also affected
by POFA replacement and immersion. In general, unsoaked masonry blocks has higher breaking load than soaked masonry
blocks. Secondly, as POFA content increases, the breaking load
decreases.
3.3.1. Effect of immersion
Similar to the compressive strength, the lower breaking load of
the soaked masonry blocks may be due to loss of strength during
submersion through water absorption that softens the matrix.
Softened matrix results in weaker bonding thus causing a weaker
masonry block that can only resist low loads.
3.3.2. Effect of POFA replacement
The breaking load of a masonry block is governed by the
tensile crack which is dependent on the bonding between the
POFA, cement and aggregate. For compressive strength, it was
discussed in the previous section that a higher POFA replacement
was related to a weaker bonding in the masonry blocks due to
possible limitations in chemical constituent in cement. A similar
reasoning may also be applied here as the breaking load decreases with the increase in POFA content. Cracks or failure for
breaking load happens at a location of weakest bond. Therefore,
the mixing process for masonry block production is very important to ensure proper blending between the POFA, cement and
aggregate. Unbalanced spread of these materials will result in
weak spots which could lead to cracking and consequently, a
lower breaking load.

140
Breaking Load, N/mm

Compressive Strength (MPa)

B1 Unsoak

Soaked

12

The breaking load of the masonry blocks is as shown in Fig. 7.
The trend observed from the Fig. 7 is comparable to those for

20
18
16
14
12
10
8
6
4
2
0

Unsoaked

14

120

Unsoaked

Soaked

100
80
60
40
20
0

0

28

56

Time (Days)

Fig. 5. Average compressive strengths of masonry blocks for batches B1 (0%) and B2
(60%) under unsoaked and soaked conditions.

0%

20%
40%
POFA Content

60%

Fig. 7. Average breaking loads of masonry blocks at 28 d under soaked and unsoaked
conditions.

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M.E. Rahman et al. / Journal of Cleaner Production 78 (2014) 195e201

3.4. Water absorption

Table 3
Efflorescence result.

The water absorption results are presentation in Fig. 8. It can be
seen that all water absorption values were below the maximum
water absorption capacity, which is 208 kg/m3 for normal weight
masonry block, 240 kg/m3 for medium weight masonry block and
320 kg/m3 for light weight masonry block in accordance with ASTM
C55-11 (ASTM Standard C55, 2011). This shows that the masonry
blocks fulfill ASTM C55-11 (ASTM Standard C55, 2011) requirement
for normal, medium or light weighted masonry blocks in terms of
water absorption. Comparing between the POFA masonry blocks
and the control masonry blocks, the water absorption of POFA
masonry blocks are observed to be slightly higher (0.1%). The
reason behind this is due to the greater porosity of POFA which tend
to favor water absorption (Safiuddin et al., 2011).
3.5. Efflorescence
Efflorescence is the formation of salt deposits on the masonry
block surfaces due to leaching of lime compounds. This is found
when water percolates through poorly compacted masonry blocks
and when evaporation takes place at the surface of the masonry
blocks. The reaction starts with the absorption of CO2 into the
masonry block. If water is presence in the masonry block, the dissolved CO2 react with lime form CaCO3 which is the visible white
salt. The efflorescence typically occurs when cool, wet weather is
followed by a dry and hot spell (Dow and Glasser, 2003; Neville,
2003).
The efflorescence results are presented in Table 3. It can be seen
from the Table 3 that there is no efflorescence. This is due to the
pozzolanic properties of POFA. One of the primary factors affecting
efflorescence is cement, where greater cement content tends to
increase the likelihood of efflorescence effects (Nawkaw, 2010).
Therefore, a higher percentage of POFA replacement leads to a
lower chance of efflorescence in the masonry blocks. Most of the
soluble salts and free lime needed for efflorescence are provided by
cement. The main chemical constituents in POFA are SiO2, Al2O3,
Fe2O3, CaO, and MgO. The SiO2 from POFA reacts with free lime
released by the hydration of Portland cement and generates Calcium Silicate Hydrate (CSH) as a gel. The CSH gel is the main binder
that holds together the aggregates reduces permeability. Thus the
lower the cement content and higher the POFA, the lower is the
possibility of efflorescence.

Batch

Water curing
condition

Testing day

Brick
condition

Efflorescence
effect

1

0

28

2

0

28

3

0

28

4

0

28

None
Immersed
None
Immersed
None
Immersed
None
Immersed

None
None
None
None
None
None
None
None

Table 4
Material cost.
Material

Cement

Sand

POFA

Cost (RM/kg)

0.285

0.024

e

cheaper since POFA is a free waste material. Consequently, less
cement is used as shown in Table 5. The higher the percentage of
replacement of cement, the cheaper the cost of the masonry block
produced. Fig. 9 shows the cost comparison of the masonry blocks
where the cement sand masonry block cost is set as the benchmark.
3.7. Comments on materials & carbon footprint
Significant amount of virgin materials, including limestone and
clay, besides energy, are consumed to produce cement and 1.5 ton
of virgin materials are needed to produce one ton of cement
(Fredrik, 1999). Cement production industries are liable for more or
less 7% of the world’s carbon dioxide discharge and to produce one
tone of cement approximately one ton of CO2 is released in the
atmosphere (Fredrik, 1999; Juan et al., 2011). This study shows that
POFA has good potential as a cement replacement up to 60% in
masonry block production. Every year significant amount POFA is
produced in Malaysia, Indonesia and Thailand. The reuse of waste
materials in masonry block is an attempt to address a part of these
problems by introducing sustainable materials in the construction
industry and consequently reduce carbon footprint.
Table 5
Unit cost of bricks.

3.6. Cost of masonry block
The cost of masonry block varies depending on the material cost.
The material costs used for comparison purposes are shown in
Table 4. From Table 4, it can be seen that the factor that changes the
cost of the masonry blocks is the cement. Comparing to the normal
cement sand masonry block, POFA masonry blocks are found to be

Batch

Cost (RM)

1
4
3
2

0.38
0.33
0.27
0.21

(0%)
(20%)
(40%)
(60%)

0.40
0.35

40.0

30.0

1.3%

1.4%
1.4%

1.3%

20.0

Cost of Brick, RM

Water Absorption (kg/m3)

50.0

0.30
0.25
0.20
0.15
0.10
0.05

10.0

0.00
0%

0.0

B1 56 Days

B1 28 Days

B2 56 Days

B2 28 Days

Fig. 8. Water absorption of different batches B1 (0%) & B2 (60%) of masonry blocks.

20%
40%
POFA Content
Fig. 9. Unit costs of bricks.

60%

M.E. Rahman et al. / Journal of Cleaner Production 78 (2014) 195e201

4. Conclusions
POFA seems to have a good potential for cement replacement in
masonry block production. The blocks can eventually be used for
construction of low-cost housing projects. Simultaneously, the use
of POFA also reduces waste materials. The following observations
and conclusions can be made on the basis of the current experimental results.
i. The compressive strength of POFA masonry block decreases
as the percentage of cement replacement increases.
Compressive strength of POFA masonry block also increases
through time but decreases when submerged into water. In
addition, POFA masonry block has lower compressive
strength compared to cement sand masonry block. However,
it satisfies the requirements of Class 1 and Class 2 loadbearing masonry block according to Malaysian Standard MS
76 (1972).
ii. The breaking load of POFA masonry block possessed a similar
pattern as compared to the compressive strength. The
breaking load also decreases with the increase of cement
replacement percentage and when submerged into water.
POFA masonry block also has lower breaking load compared
to cement sand masonry block.
iii. POFA masonry blocks have water absorption less than the
limit stated in ASTM C55-11 (2011) which is 208 kg/m3. Even
so, POFA masonry block has a slightly higher water absorption rate than cement sand masonry block.
iv. In terms of efflorescence effects, POFA masonry block and
cement sand masonry block do not show any white salt
formation on any of its surfaces and thus no efflorescence
effect is present.
v. Based on density, cement sand masonry block along with
20% and 40% POFA replacement masonry block falls under
normal weight masonry block according to ASTM C55-11
(2011). However, a 60% POFA replacement masonry block is
categorized as medium weight masonry block. Therefore,
higher replacement of cement with POFA results in lighter
weight of masonry block.
vi. The unit cost of POFA masonry block is cheaper than cement
sand masonry block as it is made of free waste material.

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